Diesel engines have been used for many years in a variety of applications, including automobiles, marine vessels and industrial generators. Diesel engines consume diesel fuel, which tends to have a higher energy density than common gasoline. Common diesel primarily consists of alkyl esters. In the past, the vast majority of diesel has been produced by refining crude oil through limited distillation/fraction procedures.
As an alternative to the petroleum-based production process, diesel can also be produced using alternative sources. The term “bio-diesel” refers to diesel that is produced from renewable sources, such as vegetable oils or animal fats. These feedstocks contain triglycerides which can be processed into alkyl esters suitable for use in diesel engines. Bio-diesel has a number of advantages over petroleum-based diesel, including lower sulfur content and improved lubricity.
Most bio-diesel production processes involve the conversion of the triglycerides into alkyl esters through a transesterification mechanism by exposing the triglycerides to an alcohol reagent (methanol) in the presence of a base catalyst (lye). Through the transesterification process, each triglyceride molecule is broken into three separate methyl ester molecules with glycerin as a by-product. To improve the quality of the bio-diesel, many production techniques include a preliminary “esterification” stage in which free fatty acids in the feedstock are converted to alkyl esters through exposure to an alcohol (e.g., methanol) in the presence of an acid (e.g., sulfuric acid).
In the past, bio-diesel production has been carried out in batch operations in which fixed quantities of reactants are processed in one or more closed reactor vessels. While generally effective at producing limited volumes of bio-diesel, batch processing is too time intensive for large-scale commercial production. As the demand for bio-diesel increases, there is a need for a continuous process capable of accommodating large-volume production. It is to this, and other deficiencies in the prior art, that the present invention is directed.